Fuses are included in semiconductor devices as in many electrical devices to help protect the devices from excessive levels of electrical current and thereby prevent damage to the devices. For example, metal fuses may be included in integrated circuits to reroute circuit features during and after wafer manufacturing processes. Some fuses are laser blown. With a laser blown fuse, laser power and spot location must be carefully controlled to minimize damage to adjacent fuses and to the underlayer structures including the semiconductor substrate.
In modern microelectronics, often, a rather large number of fuses must be incorporated into a rather small space to protect an increasingly large number of densely packed devices. For example, as memory capacity increases memory devices having similar or reduced size, the number of fuses increases.
According to one example, in currently utilized DRAM device design, the fuses typically consume an area of about 3% to about 5% of the total chip area. As device sizes continue to shrink, future generations of memory chips may be negatively impacted by the amount of area necessary for fuse structures. According to estimations, some DRAM devices may require on the order of 30,000 to 160,000 fuses.
This problem may be compounded by an increase and a need for redundancy. Accordingly, ways are being sought out to increase fuse density. One way of accomplishing an increase in fuse density is by reducing fuse pitch.
Another problem associated with fuse design is the need for providing a cavity adjacent to the fuses to provide a free volume for material displacement during fuse blowing. The free volume may also serve to limit interlevel dielectric crack propagation damage to adjacent structures.
As fuse density increases, the risk of damage to adjacent fuses may also increase.